M etallic Nanospheres

1. Oxidation of Stoichiometric and Carbon-Rich Tungsten Carbide SurfacesPetra Reinke, University of Virginia, DMR 1005809 Goal: Development of new catalysts, anode and cathode materials is critical for advancing fuel cell technology. An alternative to noble metal catalysts are transition metal carbides such as tungsten or vanadium carbides. Challenge: In transition metal carbides the surface oxidation can disrupt performance. We proposed the use of carbon rich surfaces to replenish and reduce an oxidized surface and thus retain their activity. Results : • W-carbide thin films with controlled W/C ratio • C-rich (>50 at%) with surface islands of graphene and graphite • metallic nanospheres • W-intercalated fullerene thin films This rich variety of different materials is synthesized by the change in deposition sequence (W on fullerene, fullerenes on W, and co-deposition) and temperature (300-600º C). Oxygen reactivity of carbide is relatively lowat T<400ºC, and rapidly accelerates for higher T. Bandgap maps show the spatial distribution of oxides and degree of oxidation. Petra Reinke, Assoc. Professor in Materials Science and Engineering at the University of Virginia, leads this project, which uses surface science to understand the synthesis and reactivity of transition metal carbides.

2. Oxidation of Stoichiometric and Carbon-Rich Tungsten Carbide SurfacesPetra Reinke, University of Virginia, DMR 1005809 W-C thin films on MgO(001) Metallic Nanospheres ... and Oxidation Studied with STM and STS - spatial distribution and extent of oxidation via bandgap maps W-C layers: metallic surface O2 at 300º C: uniform oxide layer – metallic with a reduced DOS at the Fermi level. O2 at 600º C: etching of graphene/graphite – complete and uniform oxidation to WO3 next experiments: early stages of oxidation – reactivity of surface and edges of graphene/graphite islands – anneal after oxidation – will the oxide be reduced? 50 nm W on 800˚C MgO W50C50 10ML C60 [30x40 nm] W40C60 Anneal 400˚C graphene on W40C60 [5x4 nm]

3. Inorganic Nanostructures Petra Reinke, University of Virginia, DMR 1005809 The book “Inorganic Nanostructures” has been published by Wiley-VCH in May 2012. It is a textbook, which introduces the exciting materials science of nanoscale materials. The book includes discussions on the quantum mechanical basis of confinement and dimensionality, and a summary of analytical techniques such as scanning probe microscopies. The major part of this book describes synthesis, and focuses then on the link between structure and properties for a multitude of inorganic materials, such as nanowires, quantum dots, and carbon based nanomaterials.